I'm suggesting a few Reader Softwares and it will be up to you to judge and choose what 's right for you. And all software are free to use. What can I say, best things in life are free.Well, not all but some..
Sumatra PDF Viewer
Sumatra PDF Viewer is very light weight, and open source. Apart from that, extremely simple to use, and very fast. It uses very less memory, and very less disk space. In fact, the download size is just 1 MB! Suitable for netbook users,I am one of the users and so far so good.
Foxit Reader
It has features such as view or print PDF document on your netbook, add or edit bookmarks in a PDF file,you can fill out PDF forms, and fill them out, you can even save filled out PDF forms and You can view PDF as Text. I did used it once but decided to stick to Sumatra instead.
Kindle for PC
Yes, for computers. However, it requires you to register with Amazon in order for you download the free ebooks. However, it seem to read only .mobi or .prc format (do correct me if I m wrong). I used it but just not to my liking. Though me being in Asia does not help I guess because I'm not able to download some ebooks
Mobipocket Ebook Reader
Something like Kindle for PC I guess, not idea as I did not try this. But reading from some reviews,it seems to better than Kindle. I must mention here that it read .mobi format and you can send it to your mobile phone,sure there are other features which are too long to read,but you are very welcome to try this.
Koobits 4.0
I m actually liking this software, why? Cause it could read PDF, EPUB, XML, HTML, KBJ and many more (at least that's whats it says in the website), though I have yet to verify the truthfulness of it (as I am only reading PDF formats). It has a good interface and it bookmarks easily. Of course, the software takes up a lot of memory space. Still, Koobits has a lot choice of free ebooks from various genre. I'd say why not give this a try. (download at : http://www.koobits.com/download.aspx)
ABC Amber Lit Converter
The software converts .lit format to other format such as .pdf, .html, .txt, among others.
I would also like to add that to those of who are too lazy to carry around too many books when you're leaving for vacation or something and looking for a good investment, get yourself a good tablet pc. There are some in the market with a reasonable price, good enough to have all your favorite books in it.
Anyway, I am not being paid to promote the above mentioned softwares. If you guys wanna try it, download it from http://download.cnet.com/windows/ or just Google it.
Have a good day!